The brain's opioid system plays an important role in reward mechanisms and recently it has been targeted in treatment efforts using the opiate antagonist, naltrexone.. Our recent findings provide strong evidence for dampened CNS opioid activity in the offspring of alcoholics, an abnormality predating heavy alcohol drinking. However, we know little about the underlying differences in the endogenous opioid system between healthy individuals and the alcohol dependent population. Indeed, little human data exists which address the question of whether there are abnormalities in the opioid system in alcohol dependent individuals and whether such differences are a consequence of genetic determinants, or a consequence of heavy alcohol use or a combination of both. The lack of knowledge of the role of endogenous opioids in alcoholism has been due primarily to difficulties in making measurements in human subjects. However, the hypothalamic-pituitary-adrenal (HPA) axis can provide useful measurements of endogenous opioid activity. This is because the HPA axis allowing a non-invasive, functional assessment of the hypothalamic opioid system. We propose to utilize this neuroendocrine strategy to measure opioid activity in alcohol dependent persons at various stages of their disorder. In Specific Aim 1, we will measure opioid activity in alcohol dependent individuals in early abstinence monitored on thje CRC and compare to controls. We will determine each subjects sensitivity to naloxone by generate a dose response curve and then calculating the dose of the naloxone required to induce a half-maximal hormone response (ED50). We will relate this measurement of opioid activity to behavioral and physiological measures such as alcohol craving, mood and alcohol withdrawal symptoms. Alcoholics and controls will be equally represented by family history positive (FHP) and family history negative (FHN) subjects. In Specific Aim II, we will measure the change in ED50 values during eight weeks of supervised abstinence on the CRC in alcohol dependent subjects compared to the control group. In Specific Aim 3 we will determine if naloxone sensitivity (ED50) measurements obtained during controlled abstinence on the CRC predicts the time to relapse after discharge. This study will provide information on the activity of the endogenous opioid system as a function of alcoholism ad as a function of family history of alcoholism. This findings will impact our understanding of the neurochemical factors that predispose to- and maintain heavy alcohol drinking.